Note: All dates from this point forward are provisional due to errors in the Imperial Calendar, meaning these events could actually have occurred at any time from the early 41st Millennium to the early 42nd Millennium.

  • Unknown Date.M42 Chaos Ascendant - In the wake of the fall of Cadia during the 13th Black Crusade and the birth of the Great Rift, a wave of Warp Storms roars into being across the length of the galaxy. Astropaths everywhere fear to open their minds to receive or broadcast messages, for the Immaterium rings with mind-splitting peals, possibly the sound of the myriad tears ripping open in the barrier between the material universe and the Warp, or perhaps the laughter of the Dark Gods...
  • Unknown Date.M42 The Noctis Aeterna - The Noctis Aeterna, also known as the "Blackness" in Low Gothic, was a catastrophic event which consumed the Milky Way Galaxy and the Imperium of Man beginning in 999.M41 and lasted at least into the second century of the 42nd Millennium. The Blackness began following the fall of Cadia at the climax of the 13th Black Crusade and the eruption of the Great Rift that cut the Imperium in half, and was marked by the loss of access to the Astronomican for FTL navigation and a disruption in all astrotelepathic communications. This period saw more devastating events consume the increasingly isolated worlds of the human-settled galaxy than at any time since the Age of Strife. Such was the turmoil during the creation of the Great Rift and the period following it that there could be no reliable accounts. As limited communications returned, Historitors and Chronotechs struggled to understand incoming reports. With the influx of Warp energies into such vast regions of realspace, time passed strangely, speeding up in some sectors, slowing in others compared to the sidereal time experienced on Terra, at the heart of the Imperium. These effects on the Warp from the birth of the Great Rift faded with the passage of time, allowing for the reestablishing of interstellar communications with some regions and somewhat more reliable Warp travel. This restoration of stability, combined with the onset of the Imperial counteroffensive known as the Indomitus Crusade, restored the grip of the Emperor over the Imperium once more. However, the price paid proved steep. Slightly less than half of the one thousand Space Marine Chapters known to operate across the galaxy remained unaccounted for, and no less than twelve Space Marine Chapter homeworlds were reported as destroyed during the Noctis Aeterna and the equally bitter campaigns that followed.
  • Unknown Date.M42 The Golden Throne is Failing - The Adeptus Mechanicus discovers that the Golden Throne has irreparable flaws that could ultimately endanger the Emperor's life. Despite the Adeptus Mechanicus' best efforts, its systems continue to fail, and no one still living knows how to repair them. Perceiving such dangerous ignorance as a manifest threat to the Emperor's safety -- and thus falling beneath the purview of the Adeptus Custodes -- Shield-Captain Heraclast Vadrian consults with Captain-General Trajann Valoris and receives permission to seek a solution. He gathers a band of his finest warriors aboard the Cruiser Scion of Argo, and sets off following a lead that points to the lost Forge World of Morvane.
  • Unknown Date.M42 Devastation of Baal - Hive Fleet Leviathan makes its final assault upon Baal, and the Blood Angels' light is nearly extinguished from the galaxy during what becomes known as the "Devastation of Baal." Salvation comes in the form of the Greater Daemon Ka'Bandha and his Blood Legions of Khornate daemons who destroyed the Tyranid swarms upon the moon of Baal Prime after the Great Rift opened, while the resurrected Primarch Roboute Guilliman's Indomitus Crusade arrived nearly simultaneously at Baal to reinforce the battered Blood Angels who had sought to make their final stand at their fortress-monastery. After many more battles, Baal was finally cleared of the xenos threat. A great rebuilding of both world and Chapter was undertaken, for the Blood Angels and their Successors were sorely needed elsewhere in the beleaguered Imperium as Guilliman named Lord Commander Dante, Chapter Master of the Blood Angels, as the Regent of the Imperium Nihilus.
  • Unknown Date.M42 Into Shadow - Upon the direct orders of Captain-General Trajann Valoris, a small, fast-moving force of Custodians makes haste for the ruined remains of Cadia. Details of their mission are suppressed, even amongst their comrades, but they are accompanied by a number of warriors drawn from the ranks of the Shield Host known as the Shadowkeepers.
  • Unknown Date.M42 The Beast Hunters - Hive Fleet Leviathan and the remaining splinter fleets from the earlier invasions of the Milky Way Galaxy by Hive Fleet Behemoth and Hive Fleet Kraken, continue to assault myriad worlds of the Imperium, slowly making their inexorable way towards Terra and the gleaming psychic beacon calling them like moths to a flame that is the Astronomican.
  • Unknown Date.M42 The Fourth Sphere Expansion is Lost - The T'au Empire's Fourth Sphere Expansion is lost in the Imperium's Eastern Fringes soon after its inception due to the effects of the Noctis Aeterna and the spiraling Warp Storms that afflict the galaxy following the birth of the Great Rift.
  • Unknown Date.M42 Rise of the Undying Legions - The Necrons continue to awaken at a rapidly increasing pace on their Tomb Worlds across the galaxy, ready to rebuild their ancient interstellar empire, and wipe away all the "lesser races" that stand in their way.
  • ca. 999.M41-111.M42 The Indomitus Crusade - The Indomitus Crusade, led by Lord Commander of the Imperium Roboute Guilliman is waged against the surging Forces of Chaos and the threats of myriad xenos such as the Orks, Tau and Eldar in the wake of the fall of Cadia during the 13th Black Crusade. Its purpose is to defend and reclaim those regions of the Imperium of Man lost in the wake of the massive tear in reality, the Great Rift, which sunders the Imperium in two, and the subsequent dire period of history known as the Noctis Aeterna.
  • ca. 005.M42 Ciaphas Cain Publishes Personal Memoirs - The famous Imperial hero, Commissar Ciaphas Cain publishes his personal memoris, To Serve the Emperor: A Commissar's Life. In his later years, Cain wished to gather and write a full accounting of his long and distinguished career. However, his more personal and candid memoir never sees the light of day and is put under Inquisitorial seal by the order of Inquisitor Amberley Vail. His personal archives contain far too many sensitive and restricted information. Undertaking the monumental task of organising Cain's files into a vast archive, she names it the Cain Archive, and publishes it for Inquisitors only. Many Inquisitors read Cain's candid accounts. Inquisitor Amberley is later persuaded to expand it considerably, making it somewhat of a bestseller amongst the agents of the Inquisition.
  • ca. 012.M42 Battle of Herodian IV - The Mantis Warriors, augmented by an Imperial Navy taskforce, comes to the aid of the beleaguered world of Herodian IV that is under attack by a large Tyranid Splinter Fleet. Despite taking a high number of casualties, the Imperials begin to turn the tide of the battle against the horde of bioform horrors, when Inquisitor Lord Brutius Parthon orders the Mantis Warriors to undertake an Exterminatus of the fallen world. This was carried out only after a Deathwatch Kill-team was extracted from a hidden Ordo Xenos weapons laboratory on the surface of the doomed planet.
  • ca. 037.M42 Cain Archive First Expanded - Orten Bassit publishes The Return of the Liberator: Ciaphas Cain and the Second Siege of Perlia. This book is later incorporated by Inquisitor Amberly Vail and used as an extract within the Cain Archive.
  • ca. 085.M42 Cain Archive Second Expansion - Stententious Logar publishes Purge the Guilty! An Imperial Account of the Liberation of Gravalax. It is later utilised by Inquisitor Amberly Vail and incorporated as an extract within the Cain Archive.
  • ca. 087.M42 Cain Archive Third Expansion - Nelson Lawford publishes Just Visitin': The Life of a Naval Hero, a biography of retired Imperial Navy Commodore Hubert Visiter. It is later utilised by Inquisitor Amberly Vail and incorporated as an extract within the Cain Archive.
  • ca. 095.M42 Cain Archive Fourth Expansion - Arten Burrar publishes The Abominable Chitin: A Concise History of the Tyrannic Wars. It is later utilised by Inquisitor Amberly Vail and incorporated as an extract within the Cain Archive.
  • ca. 097.M42 Cain Archive Fifth Expansion - Retired Lady General Jenit Sulla publishes Like a Phoenix From the Flames: The Founding of the Valhallan 597th. It is later utilised by Inquisitor Amberly Vail and incorporated as an extract within the Cain Archive.
  • ca. 101.M42 Cain Archive Sixth Expansion - Retired Lady General Jenit Sulla publishes Like a Phoenix On The Wing: The Early Campaigns and Victories of the Valhallan 597th. It is later utilised by Inquisitor Amberly Vail and incorporated as an extract within the Cain Archive.
  • ca. 111.M42 End of the Indomitus Crusade - Roboute Guilliman calls for an end to the Indomitus Crusade following the epic final battle for the Pit of Raukos. The Battle of Raukos is a two-pronged assault upon the world of 108/Beta-Kalapus-9.2 and the Warp rift known as the Pit of Raukos in Wilderness Space. The Loyalist forces quickly overwhelmed the allied Traitor Legions -- including the Word Bearers, the Iron Warriors and the Black Legion -- using the strategic location of the Warp rift to carry out assaults upon the surrounding Imperial worlds. This victory marked the end of the Indomitus Crusade and the start of Guilliman's involvement in the Plague Wars.
  • ca. 111.M42 The Plague Wars - The Plague Wars are a series of battles that occurred within the Realm of Ultramar between the forces of Nurgle, led by the Daemon Primarch Mortarion, and his Death Guard Traitor Legion against the Ultramarines, their Successor Chapters and other Imperial forces. This conflict began following the events of the 13th Black Crusade and the opening of the massive Warp rift known as the Cicatrix Maledictum. By ca. 111.M42, over a hundred standard years after the start of the Indomitus Crusade, the Imperial defenders all across Ultramar were depleted in dozens of ground campaigns, while a Plague Fleet systematically destroyed the realm's Ultramar Defence Fleet and star fortresses. Guilliman returned from the Indomitus Crusade after over a standard century of campaigning to stabilise the Imperium, and his deft and defensive manoeuvres bought time to launch what became known as the "Spear of Espandor" counterattack. The combined plague armies were eventually fought to a standstill amongst the ruins of Iax, before the Daemon Primarch Mortarion escaped with his forces back to the Scourge Stars under cover of a Virus Bomb attack, both because of his brother's staunch defence and because Nurgle's realm in realspace had come under assault by the forces of the Blood God Khorne. In a brief respite from the work of safeguarding the Emperor's realm after Mortarion's defeat, Guilliman ordered the rebuilding and decontamination of Ultramar, as well as the establishing of new procedures for creating further Primaris Ultramarines. It was not long before new Imperial Crusades called the Lord Commander of the Imperium away from Ultramar and back out into the dark galaxy. The Ultramarines then began the work of preparing their vengeance against the servants of the Dark Gods.
  • ca. 127.M42 Cain Archive Seventh Expansion - Ayjaepi Clothier publishes In Blackest Night: The Millennial Wars Appraised. It is later utilised by Inquisitor Amberly Vail and incorporated as an extract within the Cain Archive.


  • Codex Adeptus Astartes - Space Marines (8th Edition), "A Brotherhood at War," "Chronicles of Ultramar," pp. 18-19, 29
  • Codex: Adeptus Custodes (8th Edition), "The Tale of the Ten Thousand," pp. 32-33
  • Codex Heretic Astartes - Chaos Space Marines (8th Edition), "A Legacy of Hate," pg. 25
  • Gathering Storm - Part II - Fracture of Biel-Tan (7th Edition), "Addenda Inquisitoria", pg. 18
  • Warhammer 40,000: Rulebook (8th Edition), pp. 50-53
  • Warhammer 40,000: Rulebook (7th Edition)
  • The Fall of Medusa V (2006 booklet)
  • Medusa V Archive
  • Warrior Brood (Novel) by C.S. Goto
  • Kill Squad - A Deathwatch Omnibus (Omnibus) by Various Authors
  • Ciaphas Cain Series:
    • For The Emperor (Novel) by Sandy Mitchell
    • Cain's Last Stand (Novel) by Sandy Mitchell
    • Duty Calls (Novel) by Sandy Mitchell
    • The Traitor's Hand (Novel) by Sandy Mitchell
  • Dark Imperium (Novel) by Guy Haley

M41 Timeline Finis